The present invention relates to a rotation locking device locking a rotation of a rotating body by a frictional force caused by a fastening force of a coil spring.
This type of conventional rotation locking devices 100 are shown in FIGS. 8 and 9.
The rotation locking devices 100 comprise a shaft 2 extended from a flange portion 2b to be fixed on an equipment, a rotatable sleeve 3 mounted rotatably on a shaft portion 2a of the shaft 2 and a coil spring 4 closely and externally inserted over the rotatable sleeve 3. The rotatable sleeve 3 is retained by a snap ring 6 inserted into a ring ,groove formed on the outer surface of the shaft 2.
The coil spring 4 is made of round material in the manner that the free diameter thereof is smaller than the outer diameter of the sleeve 3, and is mounted on the sleeve 3 after being enlarged. The coil spring 4 has a free end 4a extended radially and another end 4b extended coaxially and inserted into the flange portion 2b.
In this case, the reverse turn of the rotatable sleeve 3 can be done easily, but the foward turn thereof can be locked by a frictional force caused by the coil spring 4. The locking force can be released by pushing the hook 4a in the unwinding direction of the coil spring 4.
However, the conventional rotation locking device has problems as follows:
(1) When the rotatable sleeve 3 is turned backward continuously, without giving a pause, the rotatable sleeve 3 is locked after being rotated some angular position, which is caused by a time delay of winding operation of the coil element C.sub.1 next to the hook 4b. The coil element C.sub.1 is wound tightly last on the shaft when the hook 4a is wound.
In order to prevent this type of play or delay, the present applicant disclosed a Japanese Patent Application No. 1-301778, wherein a rotation locking device having a coil spring 4 covered by an elastic material such as spiral spring causing a fastening force on a shaft portion, which permits a locking effect without delay because the elastic material restrains a partial enlargement of the coil spring. However, in this case, it is necessary to unlock the fastening force of the coil spring 4 because the fastening force of the elastic material works on the coil spring 4. Accordingly, when an unlocking force becomes larger, the unwinding rotation of the rotatable sleeve 3 becomes larger too, prejudicing the operability of the device.
(2) When the hook 4a is dislocated to unlock, the whole coil elements are not unwound uniformly and coil element C.sub.2 in the proximity of the hook 4a deforms largely as shown in FIGS. 9(b) and 9(c). Even when the operating force F onto the hook 4a is removed, the deformation of the coil element C.sub.2 remains and the coil element C.sub.2 floats from the rotatable sleeve 3 as indicated by "l" in FIG. 9(d), causing a delay of locking force.
The present invention was developed taking this situation into consideration and provides a rotation locking device permitting a locking operation without delay, an unlocking operation with a minor force and a smooth reverse turn of the rotatable sleeve.